Perhaps you should try some spelling variations:
"national science theories a:, life sciences" » "natural science theories a:, life sciences", "spatial science theories a:, life sciences", "animal science theories a:, life sciences", "national science three a:, life sciences"
"nato science theories a:, life sciences" » "nato science three a:, life sciences"
"radio science theories a:, life sciences" » "radio science three a:, life sciences"

Try widening your search to All Fields.

You may be able to get more results by adjusting your search query.

• If you are trying to use Boolean operators, they must be ALL CAPS: (((("nato science theories a:, life sciences") OR ((("radio science theories a:, life sciences") OR ("radio science theory a:, life sciences"))))) OR ("national science theories a:, life sciences")).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((((\"nato science theories a:, life sciences\") or (((\"radio science theories a:, life sciences\") OR (\"radio science theory a:, life sciences\"))))) or (\"national science theories a:, life sciences\"))".
• Removing quotes may allow a broader search: (((( nato science theories a:, life sciences ) or ((( radio science theories a:, life sciences ) OR ( radio science theory a:, life sciences ))))) or ( national science theories a:, life sciences )).
• Adding a wildcard symbol may retrieve word variants: (((("nato science theories a:, life sciences") or ((("radio science theories a:, life sciences") OR ("radio science theory a:, life sciences"))))) or ("national science theories a:, life sciences"))*.